Motion and Time Class 7 Worksheet Science Chapter 9

Q.1. True/False
(i) The basic unit of time is second.

True

(ii) Every object moves with a constant speed.

False

(iii) Distances between two cities are measured in kilometres.

True

(iv) The time period of a given pendulum is not constant.

False

(v) The speed of a train is expressed in m/h.

False

(vi) Clocks that measure such small time intervals are used for scientific research.

True

Q.2. Fill in the blanks.
(i)  The metallic ball is called the ____ of the pendulum.

bob

(ii) The symbols of all units are written in ____.

singular

(iii) The time taken by the pendulum to complete one oscillation is called its ____.

time period

(iv) One microsecond is one ____ of a second.

millionth

(v) A nanosecond is one ____ of a second.

billionth

(vi) The distance-time graph for the motion of an object moving with a constant speed is a ____.

straight line

Q.3. Give an example of oscillatory motion.

The to and for motion of a simple pendulum is an example of a periodic or an oscillatory motion.

Q.4. What is uniform motion?

An object moving along a straight line with a constant speed is said to be in uniform motion.

Q.5. An object moving along a straight line with a constant speed is said to be in uniform motion.

 Vehicle A is moving faster. Speed of the vehicle is greater if it covers maximum distance in a given interval of time.

Q.6. Write down the steps to draw a graph.

Steps

(i) Draw two perpendicular lines to represent the two axes and mark them as OX and OY.

(ii) Decide the quantity to be shown along the x-axis and that to be shown along the y-axis.

(iii) Choose a scale to represent the distance and another to represent the time on the graph.

(iv) Mark values for the time and the distance on the respective axes according to the scale you have chosen.
(v) Mark the points on the graph paper to represent each set of values for distance and time. Join the points.

Q.7. What is distance-time graph?

Distance-time graph represents the speed of an object.

Q.8. What is oscillatory motion?

The to and for motion of an object is called oscillatory motion.

Q.9. What is circular motion?

Circular motion is rotation of an object along a circular path.

Q.10. What is non-uniform motion?

If the speed of an object moving along a straight line keeps changing, its motion is said to be non-uniform.

Q.11. What is the basic unit of speed?

Basic unit of speed is metre per second (m/s).

Q.12.  A simple pendulum takes 32 s to complete 20 oscillations. What is the time period of the pendulum?

Number of oscillations = 20
Total time taken to complete 20 oscillations = 32 s
Time period = Total time taken/Number of oscillations = 32/20 = 1.6s

Q.13. When pendulum is said to have one complete oscillation?

The pendulum is said to have completed one oscillation when its bob, starting from its mean position B, moves to A, to C and back to B.

Q.14. What are the points that should be considered while choosing the most suitable scale for drawing a graph?

Some of the points to be kept in mind while choosing the most suitable scale for drawing a graph are:
(i) the difference between the highest and the lowest values of each quantity.
(ii) the intermediate values of each quantity, so that with the scale chosen it is convenient to mark the values on the graph, and
(iii) to utilise the maximum part of the paper on which the graph is to be drawn.

Q.15. Explain how in ancient time a day, a month and a year were measured?

Our ancestors noticed that many events in nature repeat themselves after definite intervals of time. For example, they found that the sun rises every day in the morning. The time between one sunrise and the next was called a day. Similarly, a month was measured from one new moon to the next. A year was fixed as the time taken by the earth to complete one revolution of the sun.

Q.16. The distance between two stations is 240 km. A train takes 4 hours to cover this distance. Calculate the speed of the train.

Distance between two stations = 240 km
Time taken to cover this distance = 4 hours
Speed = Distance/Time Taken = 240/4 = 60km/h

Q.17. Salma takes 15 minutes from her house to reach her school on a bicycle. If the bicycle has a speed of 2 m/s, calculate the distance between her house and the school.

Time taken = 15 min = 15 x 60 = 900 seconds
Speed = 2 m/s
Distance = Speed x Time
= 2 x 900 = 1800 m = 1800/1000 = 1.8 km

Q.18. What is the basic unit of time?

The basic unit of time is a second. Its symbol is s.

Q.19. What is speedometer?

Speedometer is an instrument that indicates the speed of a vehicle.

Q.20. What are quartz clocks?

Nowadays most clocks or watches have an electric circuit with one or more cells. These clocks are called quartz clocks. The time measured by quartz clocks is much more accurate than that by the clocks available earlier.